Problem:
Show top level taxonomy custom posts only

Solution:
To display only top level terms belongs to the taxonomy you will either have to go with custom shortcode or create a taxonomy view in classic mode (as in Block mode you can only create post type views - taxonomy and user kind views only supported in classic mode).

Relevant Documentation:

Problem: I'm trying to insert a multiline custom field into my template using the dynamic inline field feature, but I cannot find the field in dynamic sources.

Solution: Use a Single Field block instead of the inline field feature, and select the multiline field from dynamic sources in the sidebar options for the block.